Written by Dr Larry Kraizick – Bruma Lake Veterinary Clinic
Canine parvovirus (CPV) infection covers a wide spectrum when it comes to the clinical syndrome that it causes. Some dogs will develop no symptoms, while others will show sudden collapse. Between these extremes will be varying severity of vomiting, diarrhoea with or without blood; varying degrees of dehydration and electrolyte (mineral) disturbances; complications such as endotoxemia (toxins from bacteria in the blood), septicaemia (bacteria and their toxins in the blood) and intussusception (intestine telescoping into itself).
Admission into hospital is often necessary so that the dog can receive intravenous fluids, electrolytes and glucose to replace the vast quantities lost due to vomiting and diarrhoea. An intravenous drip is preferred, because the digestive tract of stricken dogs is usually in distress and can’t tolerate or absorb what the dog needs. Blood transfusions may also be helpful to boost low red blood cell counts as a result of blood loss from the gut.
Antibiotics are necessary for a dog suffering from CPV – administered first intravenously and then beneath the skin as injections – to help fight or prevent intestinal bacteria and/or their toxins entering the bloodstream. Remember, early on in the disease, the bone marrow is affected, leading to a low white blood cell count and decreased immunity. We also medicate against worms and other parasites, as these aggravate the condition.
In addition, medication to control nausea is extremely important to prevent suffering and loss of fluid and electrolytes. We also, often, give pain medication against abdominal pain. We try to feed the patient easily digested food orally as soon as possible to speed up the healing of the gut and overall recovery. Careful nursing and monitoring is the cornerstone of treatment for CPV. There are no effective antiviral drugs against CPV. Many dogs will respond to medical therapy if it’s initiated in a timely fashion, and those dogs that recover from CPV infection retain lifelong protective immunity against the strain that infected them.
CONTROL AND PREVENTION : The control of parvovirus by sanitation measures alone is extremely difficult, because the virus is such a resistant, hardy organism and is so easily spread. Contact with other dogs, especially their stool, should be minimised. Normal household bleach at one part to 30 water solutions can be used to disinfect inanimate objects such as clothing, floors, kennels, etc. This will greatly decrease the viral load present on these objects. However, it’s impractical, if not impossible, to disinfect public streets, parks, etc. Isolation of infected dogs is another method of control, although moderately effective.
Both of these measures will help reduce the amount of contagious virus in the environment, but only vaccination will control the actual source of infection, the contagious shedding dog. Dogs with CPV should be isolated (especially from pups and young dogs less than a year old and all unvaccinated dogs) during the clinical stage and for 30 days after the infection is resolved.
Vaccination is the most effective control measure for canine parvovirus disease. Although it’s not 100% effective (nothing is in life), almost all dogs that are properly vaccinated will be immune to the disease.
THE ROLE OF MATERNAL ANTIBODY IN PUPPY IMMUNISATION: Maternal antibodies are antibodies against parvovirus that are passed from the mother to the puppies through the “first milk” or colostrum. They provide the puppy with an immediate temporary or “passive” immunity. The mother obtains these antibodies from prior vaccination or by natural exposure to parvovirus.
However, the maternal antibody is a two-edged sword: it protects the puppy against disease early in life, but it also blocks active immunisation. In the case of parvovirus, the maternal antibody can interfere with vaccination for as long as 16 weeks after birth in some pups. A refractory period can exist in some pups where very low, almost undetectable levels of maternal antibody will inhibit the vaccination process but will not prevent parvovirus infection.
Since the level of maternal antibody varies from puppy to puppy, it’s important to begin vaccination at six weeks and repeat every three weeks until the puppy is at least 16 weeks old. The pup can then be vaccinated at one year of age and then every two years after that.